The ichthys is a symbol consisting of 2 intersecting arcs which resemble the profile of a fish. Its name comes from Koine Greek, meaning fish and is also known as the “sign of the fish” or “Jesus fish.” It first appeared as a symbol in the 2nd century AD. Early Christians used the ichthys to mark meeting places and tombs and to distinguish friends from foes. One tradition holds that when a Christian would meet another person he or she would draw one arc in the dirt. If the other person was also a Christian, he or she would draw a second arc to complete the symbol. It is possible the symbol’s popularity came from St. Clement of Alexandria recommending that seals be engraved with a dove or a fish. It also is believed that the fish symbol drew less attention than using a cross because fish images were used by other religious traditions as well.

For Christians, the ichthys has many symbolic meanings. Its name itself has been turned into an acrostic, a word in which each letter represents a word in a longer phrase. In Koine Greek, ichthys is written ΙΧΘΥΣ which stands for the phrase "Ἰησοῦς Χριστός, Θεοῦ Υἱός, Σωτήρ", (Iēsous Christos, Theou Yios, Sōtēr). In English, this translates as “Jesus Christ, Son of God, Saviour.” It is unknown who originally created this phrase, although it is found in St. Augustine’s 5th century work Civitate Dei, or City of God.

Fish are also frequently mentioned in the Gospels. Several of the Apostles were fishermen and were commissioned by Jesus as “fishers of men.” One of the most famous miracles, the Feeding of the 5,000, involved the multiplication of loaves and fishes as a sign of God’s ability to provide. Jesus uses the “Parable of the Drawing in the Net” to describe how God will judge mankind at the end of the world. Another miracle related to us is the miraculous catch in which Jesus tells the disciples to cast their net off the other side of their boat, resulting in a catch of 153 fish. We also read of a confrontation in which Peter is asked if Jesus pays the temple tax. Jesus tells Peter to cast his line into the lake whereupon Peter catches a fish which contains a coin sufficient to pay the tax.

In addition to these Gospel references, the fish has also been interpreted as the “sign of Jonah.” The prophet Jonah is famous for having been trapped in the belly of a large fish before embarking on his mission to Nineveh. Similarly, after His crucifixion Jesus was trapped in the tomb for three days prior to His resurrection. In this way, the fish of Jonah becomes symbolic of Christ’s resurrection and victory over death. Tertullian references both this and baptism when he writes that “we, little fishes … are born in water.”

Although an ancient symbol, the ichthys has seen a modern revival beginning in the 1970s. It is now found in many places as a symbol of modern Christianity, often with the word “Jesus” or the Greek “ΙΧΘΥΣ” inside the symbol.